Method and apparatus for casing and directional drilling using bi-centered bit

ABSTRACT

In one aspect, the present invention provides an apparatus to drill a borehole with a casing string. The casing string has affixed thereto a directional drilling assembly and a bi-centered cutter assembly. The bi-centered cutter assembly has a first cutting surface and a second cutting surface that are spaced apart by an offset. The bi-centered cutter assembly is configured to drill the borehole at a gauge diameter.

BACKGROUND OF INVENTION

Wells are generally drilled into the ground to recover natural deposits of hydrocarbons and other desirable materials trapped in geological formations in the Earth's crust. A well is typically drilled using a drill bit attached to the lower end of a “drill string.” The drill string is a long string of sections of drill pipe that are connected together end-to-end. Drilling fluid, or mud, is typically pumped down through the drill string to the drill bit. The drilling fluid lubricates and cools the drill bit, and it carries drill cuttings back to the surface in the annulus between the drill string and the borehole wall.

In conventional drilling, a well is drilled to a selected depth, and then the wellbore is typically lined with a larger-diameter pipe, usually called casing. Casing typically consists of casing sections connected end-to-end, similar to the way drill pipe is connected. To accomplish this, the drill string and the drill bit are removed from the borehole in a process called “tripping.” Once the drill string and bit are removed, the casing is lowered into the well and cemented in place. The casing protects the well from collapse and isolates the subterranean formations from each other.

Conventional drilling typically has a series of drilling, tripping, casing and cementing, and then drilling again to deepen the borehole. This process is very time consuming and costly. Additionally, other problems are often encountered when tripping the drill string. For example, the drill string may get caught up in the borehole while it is being removed. These problems require additional time and expense to correct.

FIG. 1A shows a prior art drilling operation. A drilling rig 101 and rotary table 104 at the surface are used to rotate a drill string 103 with a drill bit 105 disposed at the lower end of the drill string 103. The drill bit 105 drills a borehole 107 through subterranean formations that may contain oil and gas deposits. Typically, an MWD (measurement while drilling) or LWD (logging while drilling) collar 109 is positioned just above the drill bit 105 to take measurements relating to the properties of the formation as the borehole 107 is being drilled. In this description, MWD is used to refer either an MWD system or an LWD system. Those having ordinary skill in the art will realize that there are differences between these two types of systems, but the differences are not germane to the embodiments of the invention.

The term “casing drilling” refers to using a casing string as a drill string when drilling. A bottom hole assembly (“BHA”), comprising a drill bit, is connected to the lower end of a casing string, and the well is drilled using the casing string to transmit drilling fluid, as well as axial and rotational forces, to the drill bit. Casing drilling enables the well to be simultaneously drilled and cased.

FIG. 1B shows a prior art casing drilling operation. A rotary table 129 at the surface is used to rotate a casing string 123 that is being used as a drill string. The casing 123 extends downwardly into borehole 127. A drill bit 125 is connected to the lower end of the casing string 123. When drilling with casing, the drill bit 125 must be able to pass though the casing string 123 so that the drill bit 125 may be retrieved when drilling has been completed or when replacement or maintenance of the drill bit 125 is required. Thus, the drill bit 125 is sized smaller than the inner diameter of the casing string 123.

The drill bit 125 drills a pilot hole 128 that must be enlarged so that the casing string 123 will be able to pass through the borehole 127. An underreamer 124 is positioned below the casing string 123 and above the drill bit 125 so as to enlarge the pilot hole 128. A typical underreamer 124 can be positioned in an extended and a retracted position. In the extended position, the underreamer 124 enlarges the pilot hole 128 to the underreamed borehole 127, and in the retracted position (not shown), the underreamer 124 collapses so that it is able to pass through the inside of the casing string 123.

FIG. 1B also shows an MWD collar 135 positioned above the drill bit 125 and the underreamer 124, but below the casing string 123. The MWD collar 135 takes measurements related to formation properties as drilling is taking place. It should be noted that other positions of these BHA components are possible and are not limited to the figures shown.

Casing drilling eliminates the need to trip the drill string before the well is cased. The drill bit may simply be retrieved by pulling it up through the casing. The casing may then be cemented in place, and then drilling may continue. This reduces the time required to retrieve the BHA and eliminates the need to subsequently run casing into the well.

Another aspect of drilling is called “directional drilling.” Directional drilling is the intentional deviation of the wellbore from the path it would naturally take. In other words, directional drilling is the steering of the drill string so that it travels in a desired direction.

Directional drilling is advantageous in offshore drilling because it enables many wells to be drilled from a single platform. Directional drilling also enables horizontal drilling through a reservoir. Horizontal drilling enables a longer length of the wellbore to traverse the reservoir, which increases the production rate from the well.

A directional drilling system may also be used in vertical drilling operation as well. Often the drill bit will veer off of an planned drilling trajectory because of the unpredictable nature of the formations being penetrated or the varying forces that the drill bit experiences. When such a deviation occurs, a directional drilling system may be used to put the drill bit back on course.

One method of directional drilling uses a bottom hole assembly (“BHA”) that includes a bent housing and a mud motor. A bent housing 200 is shown in FIG. 2A. The bent housing 200 includes an upper section 203 and a lower section 204 that are formed on the same drill collar assembly, but are separated by a bend 201. The bend 201 is a surface adjustable mechanical joint in the drill collar assembly.

With a bent housing 200, the drill string is not rotated from the surface. Instead, the drill bit 205 is pointed in the desired drilling direction, and the drill bit 205 is rotated by a mud motor (not shown) located in the BHA. A mud motor converts some of the energy of the mud flowing down through the drill pipe into a rotational motion that drives the drill bit 205. Thus, by maintaining the bent housing 200 at the same azimuthal position with respect to the borehole, the drill bit 205 will drill in the desired direction.

When straight drilling is desired, the entire drill string, including the bent housing 200, is rotated from the surface. The drill bit 205 angulates with the bent housing 200 and drills a slightly overbore, but straight, borehole (not shown).

Another method of directional drilling has the use of a rotary steerable system (“RSS”). In an RSS, the drill string is rotated from the surface, and downhole devices cause the drill bit to drill in the desired direction. Rotating the drill string greatly reduces the occurrences of the drill string getting hung up or stuck during drilling.

Generally, there are two types of RSS's—“point-the-bit” systems and “push-the-bit” systems. In a point-the-bit system, the drill bit is pointed in the desired direction of the borehole deviation, similar to a bent housing. In a push-the-bit system, devices on the BHA push the drill bit laterally in the direction of the desired borehole deviation by pressing on the borehole wall.

A point-the-bit system works in a similar manner to a bent housing because a point-the-bit system typically includes a mechanism for providing a drill bit alignment that is different from the drill string axis. The primary differences are that a bent housing has a bend at a fixed angle set on the surface and fly coupled and aligned with the drill string rotation, and a point-the-bit RSS has a bend angle that is controlled independently of the drill string rotation.

FIG. 2B shows a point-the-bit RSS 210. A point-the-bit RSS 210 typically has an drill collar 213 and a drill bit shaft 214. The drill collar 213 has an internal orientating and control mechanism (not shown) that counter-rotates relative to the drill string. This internal mechanism controls the angular orientation of the drill bit shaft 214 relative to the borehole (not shown).

The angle θ between the drill bit shaft 214 and the drill collar 213 may be selectively controlled. The angle θ shown in FIG. 2B is exaggerated for purposes of illustration. A typical angle is less than 2 degrees.

The “counter rotating” mechanism rotates in the opposite direction of the drill string rotation. Typically, the counter rotation occurs at the same speed as the drill string rotation so that the counter rotating section maintains the same angular position relative to the inside of the borehole. Because the counter rotating section does not rotate with respect to the borehole, it is often called “geo-stationary” by those skilled in the art. In this disclosure, no distinction is made between the terms “counter rotating” and “geo-stationary.”

A push-the-bit system typically uses either a rotating or non-rotating stabilizer and/or pad arrangement. The non-rotating stabilizer and/or actuated pad remains at a fixed angle (or geo-stationary) with respect to the borehole wall. When the borehole is to be deviated, an actuator presses a pad against the borehole wall in the opposite direction from the desired deviation. The result is that the drill bit is pushed or actuated in the desired direction.

FIG. 2C shows a typical push-the-bit system 220. The drill string 223 includes rotating collar 221 that includes one or more extendable and retractable pads 226. When a pad 226 is extended into contact with the borehole (not shown) during drilling, the drill bit 225 is pushed in the opposite direction, enabling the drilling of a deviated borehole.

FIG. 3 shows a prior art drilling system that has both casing drilling and directional drilling. A rotary table 304 is used to rotate a casing string 311 that is being used as a drill string. A drill bit 305 and an underreamer 313 are positioned at the lower end of the casing string 311. The drill bit 305 drills a pilot hole 308 that is enlarged to an underreamed borehole 307 by the underreamer 313.

The casing drilling system also has an RSS 315 that is positioned blow the casing string 311 and between the drill bit 305 and the underreamer 313. The RSS 315 is used to change the direction of the drill bit 305.

Nonetheless, a need still exists for an improved drilling system.

SUMMARY OF INVENTION

An embodiment of the present invention provides an apparatus to drill a borehole with a drillstring. The drillstring has a directional drilling assembly connected to its distal end. The directional drilling assembly has a rotary steerable system, a mud motor, and a bi-centered cutter assembly. The bi-centered cutter assembly has a first cutting surface and a second cutting surface that are spaced apart by an offset. The bi-centered cutter assembly is configured to drill the borehole at a gauge diameter.

Another embodiment of the present invention provides an apparatus to drill a borehole with a casing string. The apparatus comprises a directional drilling assembly, a casing latch, and a bi-centered cutter assembly. The directional drilling assembly is connected at a distal end of the casing string. The casing latch is installed at the distal end of the casing string between the casing string and the directional drilling assembly. The casing latch has a pass-through diameter smaller than the inner diameter of the casing string. The bi-centered cutter assembly is configured to be retrieved through the pass-through diameter of the casing latch. The bi-centered cutter assembly has a first cutting surface and a second cutting surface that are offset from one another. The bi-centered cutting assembly is configured to drill the borehole at a gauge diameter that is larger than the pass-through diameter of the casing latch.

Another embodiment of the present invention provides a method to drill a borehole with a drillstring. The method comprises attaching a drilling assembly to a distal end of the drillstring. The drilling assembly has a rotary steerable system and a bi-centered cutter assembly. The method further comprises rotating and axially loading the casing string and attached bi-centered cutter assembly to drill a first section of the borehole. The method further comprises orienting the bi-centered cutter assembly with the rotary steerable system. The method further comprises sliding the drillstring deeper into the borehole as it is drilled.

Another embodiment of the present invention provides a method to install a casing string into a borehole while drilling. The method comprises attaching a drilling assembly to a distal end of the casing string. The drilling assembly is releasably attached to the casing string by a casing latch having a pass-through diameter smaller than an inner diameter of the casing string. The method further comprising connecting a bi-centered cutter assembly to a distal end of the drilling assembly. The bi-centered cutter assembly is configured to drill the borehole at a gauge diameter that is larger than an outer diameter of the casing string. A first section of the borehole is drilled. The casing string is slid further into the borehole as it is drilled. The drilling assembly is released from the casing latch and the drilling assembly and the bi-centered cutter assembly are retrieved through the casing latch and the casing string. Finally, the casing string is cemented in place.

Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1B shows a prior art drilling operation.

FIG. 1B shows a prior art casing drilling operation.

FIG. 2A shows a prior art bent housing.

FIG. 2B shows a prior art “point-the-bit” system.

FIG. 2C shows a prior art “push-the-bit” system.

FIG. 3 shows a prior art directional casing drilling operation.

FIG. 4 shows a directional casing drilling system having a bi-centered bit in accordance with one embodiment of the invention.

FIG. 5 shows a rotary steerable directional casing drilling system having a bi-centered bit in accordance with another embodiment of the invention.

FIG. 6 shows a rotary steerable directional casing drilling system having a bi-centered bit in accordance with another embodiment of the invention.

FIG. 7 shows a bi-centered bit in accordance with another embodiment of the invention.

FIG. 8 shows a bi-centered bit in accordance with another embodiment of the invention.

DETAILED DESCRIPTION

In some embodiments, the invention relates to the use of a bi-centered bit in a directional casing drilling system. In some other embodiments, the invention relates to the use of a bi-centered bit in a rotary steerable casing drilling system. In yet other embodiments, the invention relates to the use of bi-centered bits in a rotary steerable system (RSS).

It should be noted that although specific embodiments refer to casing drilling, the teachings of the present invention are equally applicable to drilling while lining. A “liner” is a casing string that does not extend to the top of a well. A liner is typically used when a well is drilled, cased, and then drilled again to deepen the well. The part of the well that is drilled past the initial casing string is cased with “liner.” In practice, the only difference between casing and liner is that the liner has a smaller diameter, and it is suspended from the bottom of the casing string above it. The difference between liner and casing is not germane to the invention; thus, no distinction is made between casing and liner.

Referring now to FIG. 4, a schematic representation of a directional casing drilling system 450 using a bi-centered cutter assembly 452 is shown. The directional casing drilling assembly 450 has a bottom hole assembly (BHA) 420 that is connected to the casing string 424 through a casing latch 426. In an embodiment of the present invention, the traditional drill bit and underreamer of the BHA 420 have been replaced by the bi-centered cutter assembly 452.

The illustrated BHA 420 additionally comprises a mud motor and bent sub assembly 432, a measurement while drilling (MWD) assembly 434, and an eccentric bushing 436. However, it should be understood that the component make-up of the BHA 420 is not intended to limit the scope of the present invention.

The bi-centered cutter assembly 452 has the benefit of cutting the same diameter bore 454 as would be possible with a traditional bit and underreamer, but without the need for engaging and collapsing the cutting arms of the underreamer. The bi-centered cutting assembly 452 preferably has two cutting surfaces, a first cutting surface 456 and a second cutting surface 458 axially spaced by an offset. The first cutter surface 456 effectively cuts a pilot hole 460 while second cutter surface 458, eccentrically positioned around the rotation axis of bit 452 and cutting surface 456, performs the underreaming function and finish cuts the primary bore 454.

One of the benefits of using a bi-centered cutting assembly over a traditional bit and collapsible underreamer is that the task of extending the cutter arms of the underreamer is no longer necessary. Furthermore, there no longer is a risk that the arms of the underreamer will become damaged or broken, thereby necessitating a costly fishing and recovery operation. Additionally, the risk of the underreamer becoming damaged and un-retrievable through the casing latch 426 is avoided as the bi-centered cutting assembly 452 is designed to be retrieved through the same casing latch 426, but without the need for an intervening configuration step.

Referring now to FIG. 5, a schematic representation of a directional casing drilling assembly 570 using a bi-centered cutter assembly 552 with a point the bit RSS is shown. The directional casing drilling assembly 570 is similar to that shown in FIG. 4, except that a point the bit rotary steerable directional casing drilling system 572 is used in place of the bent housing (432 of FIG. 4) to guide the bi-centered cutter assembly 552 to its desired trajectory. Also in the directional casing drilling system 572 is a MWD assembly 574 to communicate to controllers or personnel on the surface how and where to direct drilling operations with the direction casing drilling assembly 572.

Using the point the bit system 572, the bit axis 576 needed for the desired trajectory of the wellbore 578 is maintained, while the casing string 524 is rotated. This is accomplished through the use of a geostationary angular orientation device that acts in a manner similar to a bent housing. While the casing string 524 (and attached bi-centered cutting assembly 552) is rotated, the angular orientation device (not shown) is capable of not rotating with respect to the borehole, thus allowing the angle of the RSS to remain in place while the casing string 524 is rotated from above to drill first a pilot hole 578 and then the completed full gauge borehole 580.

When the borehole 580 is completed, the casing latch 526 can be disengaged and the entire directional casing drilling assembly 570 can be retrieved through the internal bore of the casing string 524. After the directional casing drilling assembly is removed, a cementing operation can be performed to secure the casing string 524 in place.

It should be understood that the point the bit system 575 having the bi-centered bit 552 is fully compatible with traditional drillstring if casing while drilling is not desired.

Referring to FIG. 6, a schematic representation of a push the bit rotary steerable directional casing drilling assembly 690 using a bi-centered cutter assembly 652 is shown. The drilling assembly 690 has the MWD assembly 574 of FIG. 5, but uses a push the bit RSS 692. The push the bit RSS 692 also has an outer profile that houses at least one kick pad apparatus 694 to steer the drilling of the pilot hole 696 and the completed borehole 698. Because the kick pad 694 is synchronously and sequentially activated at the same location relative to the borehole 698 while the casing string 624 and RSS 692 is rotated, dynamic pushing and positioning of the bi-centered cutting assembly 652 is possible. The push the bit system 690 is retrievable through the casing latch 626. Another variant of the push the bit system is one with a stationary, non-rotating, sliding sleeve and kick-pad assembly.

As with the point the bit system 570 of FIG. 5, the push the bit system 690 is fully compatible with a traditional drillstring if casing while drilling is not desired. If using traditional drillstring, the entire drillstring must first be “tripped out” of the before a casing string can be subsequently installed, if desired.

Referring now to FIG. 7, a schematic representation of a first bi-centered cutter assembly 700 is shown. The bi-centered cutter assembly 700 is shown attached to a directional drilling assembly 702 to cut a borehole 704. While no particular directional drilling assembly 702 is shown, it should be understood that directional drilling assembly 702 may have a bent housing, a point the bit RSS, a push the bit RSS, or any other type of directional drilling assembly known to one skilled in the art. The bi-centered cutter assembly has a first cutter 706 and a second cutter assembly 708. The first and second cutter assemblies 706, 708 are not co-axial and are instead axially spaced by an offset (not shown). The first cutter 706 is responsible for cutting a pilot hole 710 and the second cutter assembly is responsible for cutting a region 712 to open up the pilot hole into the full bore 702. Depending on the type and configuration of the directional drilling assembly 702 used, a kick pad or stabilizer 714 can press against borehole 704 to keep the bi-centered cutting assembly 700 on path.

Referring now to FIG. 8, a schematic representation of a second bi-centered cutter assembly 820 is shown. The bi-centered cutter assembly 820 has a first cutter m surface in the form of a traditional drill bit 822 along its axis to cut a pilot hole 824. A second cutter surface 826 is positioned upon a distal end of a directional drilling assembly 828 to open up a pilot hole 824 through a region 830 into a full desired bore 832. As above, it should be understood that the directional drilling assembly 828 may have a bent housing, a point the bit RSS, a push the bit RSS, or any other type of directional drilling assembly known to one skilled in the art. Also, depending on the type and configuration of the directional drilling assembly 828 used, a kick pad or stabilizer 834 can be employed to press against the borehole 832 to keep the bi-centered cutting assembly 820 on path.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 

1. An apparatus to drill a borehole with a drillstring, the drillstring having an internal bore and an external diameter, the apparatus comprising: the drillstring having a directional drilling assembly connected at a distal end; said directional drilling assembly having a rotary steerable system, a mud motor, and a bi-centered cutter assembly; said bi-centered cutter assembly having a first cutting surface and a second cutting surface, wherein said first and said second cutting surfaces are spaced apart by an offset; and said bi-centered cutter assembly configured to drill the borehole at a gauge diameter.
 2. The apparatus of claim 1 wherein the drillstring is a casing string, said casing string having a inner casing diameter and an outer casing diameter.
 3. The apparatus of claim 2 wherein said casing string has a casing latch installed at said distal end between said casing string and said directional drilling assembly, said casing latch having a pass-through diameter smaller than said inner casing diameter.
 4. The apparatus of claim 3 wherein said bi-centered cutter assembly is configured to be retrieved through said pass-through diameter of said casing latch.
 5. The apparatus of claim 4 wherein said gauge diameter is larger than said pass-through diameter.
 6. The apparatus of claim 1 wherein said directional drilling assembly further has directional measurement equipment.
 7. The apparatus of claim 6 wherein said directional measurement equipment is selected from the group consisting of measurement while drilling tools, accelerometers, magnetometers, and gyroscopes.
 8. The apparatus of claim 1 wherein the mud motor is a positive displacement mud motor.
 9. The apparatus of claim 1 wherein the mud motor is a turbine mud motor.
 10. The apparatus of claim 1 wherein said rotary steerable system and said mud motor are contained within a single housing.
 11. The apparatus of claim 1 wherein said rotary steerable system is a push the bit rotary steerable system.
 12. The apparatus of claim 11 wherein said rotary steerable system has at least one synchronous and sequentially actuated peripheral pad to press against the borehole and push the bi-centered cutter assembly in a desired direction.
 13. The apparatus of claim 11 wherein said rotary steerable system has at least one peripheral pad in a non-rotating, sliding sleeve assembly provided to press against the borehole and push the bi-centered cutter assembly in a desired direction.
 14. The apparatus of claim 1 wherein said rotary steerable system is a point the bit rotary steerable system.
 15. The apparatus of claim 14 wherein said rotary steerable system has a geostationary angular orientation device to point said bi-centered cutter assembly in a desired direction.
 16. The apparatus of claim 1 wherein said first cutting surface is a standard drill bit located on a central axis of said directional drilling assembly.
 17. The apparatus of claim 16 wherein said second cutting surface is located on a peripheral surface of said directional drilling assembly, wherein a center of rotation of said peripheral surface is displaced from said central axis by said offset.
 18. An apparatus to drill a borehole with a casing string, the casing string having an internal diameter and an external diameter, the apparatus comprising: a directional drilling assembly connected at a distal end of the casing string; a casing latch installed at said distal end between the casing string and said directional drilling assembly, said casing latch having a pass-through diameter smaller than the internal diameter of the casing string; a bi-centered cutter assembly, wherein said bi-centered cutter assembly is configured to be retrieved through said pass-through diameter of said casing latch; said bi-centered cutter assembly having a first cutting surface and a second cutting surface, wherein said first and said second cutting surfaces are spaced apart by an offset; and said bi-centered cutter assembly configured to drill the borehole at a gauge diameter, wherein said gauge diameter is larger than said pass-through diameter of said casing latch.
 19. The apparatus of claim 18 further comprising a mud motor.
 20. The apparatus of claim 19 wherein said mud motor is selected from the group consisting of positive displacement mud motors and turbine mud motors.
 21. The apparatus of claim 18 wherein said directional drilling assembly has directional measurement equipment.
 22. The apparatus of claim 21 wherein said directional measurement equipment is selected from the group consisting of measurement while drilling tools, accelerometers, magnetometers, and gyroscopes.
 23. The apparatus of claim 18 wherein said directional drilling assembly has a rotary steerable system.
 24. The apparatus of claim 23 wherein said rotary steerable system is a push the bit rotary steerable system.
 25. The apparatus of claim 24 further comprising at least one synchronous and sequentially actuated peripheral pad to press against the borehole and push the bi-centered cutter assembly in a desired direction.
 26. The apparatus of claim 24 wherein said rotary steerable system has at least one peripheral pad in a non-rotating, sliding sleeve assembly provided to press against the borehole and push the bi-centered cutter assembly in a desired direction.
 27. The apparatus of claim 23 wherein said rotary steerable system is a point the bit rotary steerable system.
 28. The apparatus of claim 27 further comprising a geostationary angular orientation device to point said bi-centered cutter assembly in a desired direction.
 29. The apparatus of claim 18 wherein said first cutting surface is a standard drill bit located on a central axis of said directional drilling assembly.
 30. The apparatus of claim 29 wherein said second cutting surface is located on a peripheral surface of said directional drilling assembly, wherein a center or rotation of said peripheral surface is displaced from said central axis by said offset.
 31. The apparatus of claim 30 wherein said first cutting surface is rotated by a mud motor.
 32. A method to drill a borehole with a drillstring, the method comprising: attaching a drilling assembly to a distal end of the drillstring, the drilling assembly having a rotary steerable system and a bi-centered cutter assembly; rotating and axially loading the casing string and attached bi-centered cutter assembly to drill a first section of the borehole; orienting the bi-centered cutter assembly with the rotary steerable system; sliding the drillstring deeper into the borehole as it is drilled.
 33. The method of claim 32 wherein the rotary steerable system is a push the bit rotary steerable system.
 34. The method of claim 33 further comprising pressing at least one synchronous and sequentially actuated peripheral pad against the borehole to push the bi-centered cutter assembly to drill a second section of the borehole in a desired direction.
 35. The apparatus of claim 31 wherein said rotary steerable system has at least one peripheral pad in a non-rotating, sliding sleeve assembly provided to press against the borehole and push the bi-centered cutter assembly in a desired direction.
 36. The method of claim 32 wherein the rotary steerable system is a point the bit rotary steerable system.
 37. The method of claim 36 further comprising pointing the bi-centered cutter assembly with a geostationary angular orientation device to drill a second section of the borehole in a desired direction.
 38. The method of claim 32 wherein the bi-centered cutter assembly has a first cutting surface and a second cutting surface, wherein the first and the second cutting surfaces are spaced apart by an offset.
 39. The method of claim 38 wherein the first cutting surface is a standard drill bit located on a central axis of the drilling assembly.
 40. The method of claim 38 wherein the second cutting surface is located on a peripheral surface of the drilling assembly, wherein a center of rotation of the peripheral surface is displaced from a central axis of the drilling assembly by the offset.
 41. The method of claim 32 wherein the drillstring is a casing string wherein the casing string has a inner diameter and an outer diameter.
 42. The method of claim 41 further comprising installing a casing latch at the distal end between the casing string and the drilling assembly, the casing latch having a pass-through diameter smaller than the inner diameter of the casing string.
 43. The method of claim 42 comprising retrieving the bi-centered cutter assembly through the pass-through diameter of the casing latch.
 44. A method to install a casing string into a borehole while drilling, the method including: attaching a drilling assembly to a distal end of the casing string, the drilling assembly releasably connected to the casing string by a casing latch having a pass-through diameter wherein the pass-through diameter is smaller than an inner diameter of the casing string; connecting a bi-centered cutter assembly to a distal end of the drilling assembly, the bi-centered cutter assembly configured to drill the borehole at a gauge diameter, wherein the gauge diameter is larger than an outer diameter of the casing string; drilling a first section of the borehole; sliding the casing string further into the borehole as it is drilled; releasing the drilling assembly from the casing latch; retrieving the drilling assembly and the bi-centered cutter assembly through the casing latch and the casing string; and cementing the casing string in place.
 45. The method of claim 44 including rotating the bi-centered cutter assembly with a mud motor.
 46. The method of claim 44 including rotating the casing string, drilling assembly, and attached bi-centered cutter assembly from the surface.
 47. The method of claim 46 wherein the drilling assembly includes a rotary steerable system.
 48. The method of claim 47 wherein the rotary steerable system is a push the bit rotary steerable system.
 49. The method of claim 48 further including pressing at least one synchronous and sequentially actuated peripheral pad against the borehole to push the bi-centered cutter assembly in a desired direction to drill a second section of the borehole.
 50. The apparatus of claim 48 wherein said rotary steerable system has at least one peripheral pad in a non-rotating, sliding sleeve assembly to press against the borehole and push the bi-centered cutter assembly in a desired direction.
 51. The method of claim 47 wherein the rotary steerable system is a point the bit rotary steerable system.
 52. The method of claim 51 further including using a geostationary angular orientation device to point the bi-centered cutter assembly in a desired direction to drill a second section of the borehole. 